Presently, operating rooms are being increasingly equipped with so called navigation systems. These navigation systems help operating physicians determine a positional relationship between treatment devices (e.g., instruments) and patients or parts of a patient's body. The navigation systems also can provide treatment-assisting image outputs.
In order to provide functioning navigation, it is necessary to determine and track the positions of the treatment devices and/or treatment-assisting devices and the patient in a predefined coordinate system. This process is called “tracking”. There are optical or magnetic tracking systems that can locate and track reference markers or reference marker arrays, which may be attached to the treatment devices and/or to the patient. However, it is also possible, for example, to position a tracked instrument on other objects or parts of the patient, and then identify the location of the object based on a known location of the instrument. Another type of tracking system can specifically be used for manipulators such as, for example, medical or surgical robots, wherein sensors are coupled to joints of said manipulators. The sensors can ascertain movement of the manipulators and, therefore, movement of an instrument attached to the manipulator (e.g., relative to a pre-calibrated zero position).
Using such position detection devices for redundant position measuring is known. In such systems, for example “external data” obtained via a camera tracking system that tracks reference marker arrays attached to an object of interest can be transformed into a robot coordinate system and used as input data for controlling the robot. The robot, which can include an “internal tracking system”, e.g., a joint sensor tracking system, detects its own tracking data, and the redundancy of the joint sensor data and the data of the external tracking system can be used to compensate for a failure of a tracking data source. In this manner, treatment and/or treatment assistance does not have to be interrupted. If the data of the redundant position detection devices do not match, the treatment assistance and/or operation of the robot can be halted, the movement of a joint arm may be stopped, or the operation of an active tool may be discontinued.
A method is known from U.S. Pat. No. 6,547,782 B1 that limits the movement of an instrument attached to a robot within a patient to a predetermined plan. The use of redundant joint sensors is disclosed.
EP 0 456 103 A3 and/or U.S. Pat. No. 5,086,401 disclose a method for a redundant consistency check on a surgical robot, with position control of a tool and safety monitoring of the position of the tool by a camera system. The operational status is periodically monitored, and means are provided for preventing further movement of the tool when the operational status is not optimum.
Redundant position detection has thus hitherto been used to improve the safety of automatic or guided treatment procedures by halting the treatment in different detected positions or replacing one position data source with another position data source when the first fails.